use anyhow::{Context as _, Result, anyhow};
use futures::{AsyncBufReadExt, AsyncReadExt, StreamExt, io::BufReader, stream::BoxStream};
use http_client::{AsyncBody, HttpClient, Method, Request as HttpRequest, http};
use serde::{Deserialize, Serialize};
use serde_json::Value;
use std::{convert::TryFrom, time::Duration};

pub const LMSTUDIO_API_URL: &str = "http://localhost:1234/api/v0";

#[derive(Clone, Copy, Serialize, Deserialize, Debug, Eq, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum Role {
    User,
    Assistant,
    System,
    Tool,
}

impl TryFrom<String> for Role {
    type Error = anyhow::Error;

    fn try_from(value: String) -> Result<Self> {
        match value.as_str() {
            "user" => Ok(Self::User),
            "assistant" => Ok(Self::Assistant),
            "system" => Ok(Self::System),
            "tool" => Ok(Self::Tool),
            _ => anyhow::bail!("invalid role '{value}'"),
        }
    }
}

impl From<Role> for String {
    fn from(val: Role) -> Self {
        match val {
            Role::User => "user".to_owned(),
            Role::Assistant => "assistant".to_owned(),
            Role::System => "system".to_owned(),
            Role::Tool => "tool".to_owned(),
        }
    }
}

#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
#[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq)]
pub struct Model {
    pub name: String,
    pub display_name: Option<String>,
    pub max_tokens: u64,
    pub supports_tool_calls: bool,
    pub supports_images: bool,
}

impl Model {
    pub fn new(
        name: &str,
        display_name: Option<&str>,
        max_tokens: Option<u64>,
        supports_tool_calls: bool,
        supports_images: bool,
    ) -> Self {
        Self {
            name: name.to_owned(),
            display_name: display_name.map(|s| s.to_owned()),
            max_tokens: max_tokens.unwrap_or(2048),
            supports_tool_calls,
            supports_images,
        }
    }

    pub fn id(&self) -> &str {
        &self.name
    }

    pub fn display_name(&self) -> &str {
        self.display_name.as_ref().unwrap_or(&self.name)
    }

    pub fn max_token_count(&self) -> u64 {
        self.max_tokens
    }

    pub fn supports_tool_calls(&self) -> bool {
        self.supports_tool_calls
    }
}

#[derive(Debug, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum ToolChoice {
    Auto,
    Required,
    None,
    #[serde(untagged)]
    Other(ToolDefinition),
}

#[derive(Clone, Deserialize, Serialize, Debug)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum ToolDefinition {
    #[allow(dead_code)]
    Function { function: FunctionDefinition },
}

#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct FunctionDefinition {
    pub name: String,
    pub description: Option<String>,
    pub parameters: Option<Value>,
}

#[derive(Serialize, Deserialize, Debug)]
#[serde(tag = "role", rename_all = "lowercase")]
pub enum ChatMessage {
    Assistant {
        #[serde(default)]
        content: Option<MessageContent>,
        #[serde(default, skip_serializing_if = "Vec::is_empty")]
        tool_calls: Vec<ToolCall>,
    },
    User {
        content: MessageContent,
    },
    System {
        content: MessageContent,
    },
    Tool {
        content: MessageContent,
        tool_call_id: String,
    },
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
#[serde(untagged)]
pub enum MessageContent {
    Plain(String),
    Multipart(Vec<MessagePart>),
}

impl MessageContent {
    pub fn empty() -> Self {
        MessageContent::Multipart(vec![])
    }

    pub fn push_part(&mut self, part: MessagePart) {
        match self {
            MessageContent::Plain(text) => {
                *self =
                    MessageContent::Multipart(vec![MessagePart::Text { text: text.clone() }, part]);
            }
            MessageContent::Multipart(parts) if parts.is_empty() => match part {
                MessagePart::Text { text } => *self = MessageContent::Plain(text),
                MessagePart::Image { .. } => *self = MessageContent::Multipart(vec![part]),
            },
            MessageContent::Multipart(parts) => parts.push(part),
        }
    }
}

impl From<Vec<MessagePart>> for MessageContent {
    fn from(mut parts: Vec<MessagePart>) -> Self {
        if let [MessagePart::Text { text }] = parts.as_mut_slice() {
            MessageContent::Plain(std::mem::take(text))
        } else {
            MessageContent::Multipart(parts)
        }
    }
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum MessagePart {
    Text {
        text: String,
    },
    #[serde(rename = "image_url")]
    Image {
        image_url: ImageUrl,
    },
}

#[derive(Serialize, Deserialize, Clone, Debug, Eq, PartialEq)]
pub struct ImageUrl {
    pub url: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub detail: Option<String>,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct ToolCall {
    pub id: String,
    #[serde(flatten)]
    pub content: ToolCallContent,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
#[serde(tag = "type", rename_all = "lowercase")]
pub enum ToolCallContent {
    Function { function: FunctionContent },
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct FunctionContent {
    pub name: String,
    pub arguments: String,
}

#[derive(Serialize, Debug)]
pub struct ChatCompletionRequest {
    pub model: String,
    pub messages: Vec<ChatMessage>,
    pub stream: bool,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub max_tokens: Option<i32>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub stop: Option<Vec<String>>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub temperature: Option<f32>,
    #[serde(skip_serializing_if = "Vec::is_empty")]
    pub tools: Vec<ToolDefinition>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub tool_choice: Option<ToolChoice>,
}

#[derive(Serialize, Deserialize, Debug)]
pub struct ChatResponse {
    pub id: String,
    pub object: String,
    pub created: u64,
    pub model: String,
    pub choices: Vec<ChoiceDelta>,
}

#[derive(Serialize, Deserialize, Debug)]
pub struct ChoiceDelta {
    pub index: u32,
    pub delta: ResponseMessageDelta,
    pub finish_reason: Option<String>,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct ToolCallChunk {
    pub index: usize,
    pub id: Option<String>,

    // There is also an optional `type` field that would determine if a
    // function is there. Sometimes this streams in with the `function` before
    // it streams in the `type`
    pub function: Option<FunctionChunk>,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct FunctionChunk {
    pub name: Option<String>,
    pub arguments: Option<String>,
}

#[derive(Serialize, Deserialize, Debug)]
pub struct Usage {
    pub prompt_tokens: u64,
    pub completion_tokens: u64,
    pub total_tokens: u64,
}

#[derive(Debug, Default, Clone, Deserialize, PartialEq)]
#[serde(transparent)]
pub struct Capabilities(Vec<String>);

impl Capabilities {
    pub fn supports_tool_calls(&self) -> bool {
        self.0.iter().any(|cap| cap == "tool_use")
    }

    pub fn supports_images(&self) -> bool {
        self.0.iter().any(|cap| cap == "vision")
    }
}

#[derive(Serialize, Deserialize, Debug)]
pub struct LmStudioError {
    pub message: String,
}

#[derive(Serialize, Deserialize, Debug)]
#[serde(untagged)]
pub enum ResponseStreamResult {
    Ok(ResponseStreamEvent),
    Err { error: LmStudioError },
}

#[derive(Serialize, Deserialize, Debug)]
pub struct ResponseStreamEvent {
    pub created: u32,
    pub model: String,
    pub object: String,
    pub choices: Vec<ChoiceDelta>,
    pub usage: Option<Usage>,
}

#[derive(Deserialize)]
pub struct ListModelsResponse {
    pub data: Vec<ModelEntry>,
}

#[derive(Clone, Debug, Deserialize, PartialEq)]
pub struct ModelEntry {
    pub id: String,
    pub object: String,
    pub r#type: ModelType,
    pub publisher: String,
    pub arch: Option<String>,
    pub compatibility_type: CompatibilityType,
    pub quantization: Option<String>,
    pub state: ModelState,
    pub max_context_length: Option<u64>,
    pub loaded_context_length: Option<u64>,
    #[serde(default)]
    pub capabilities: Capabilities,
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum ModelType {
    Llm,
    Embeddings,
    Vlm,
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "kebab-case")]
pub enum ModelState {
    Loaded,
    Loading,
    NotLoaded,
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum CompatibilityType {
    Gguf,
    Mlx,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct ResponseMessageDelta {
    pub role: Option<Role>,
    pub content: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub reasoning_content: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub tool_calls: Option<Vec<ToolCallChunk>>,
}

pub async fn complete(
    client: &dyn HttpClient,
    api_url: &str,
    request: ChatCompletionRequest,
) -> Result<ChatResponse> {
    let uri = format!("{api_url}/chat/completions");
    let request_builder = HttpRequest::builder()
        .method(Method::POST)
        .uri(uri)
        .header("Content-Type", "application/json");

    let serialized_request = serde_json::to_string(&request)?;
    let request = request_builder.body(AsyncBody::from(serialized_request))?;

    let mut response = client.send(request).await?;
    if response.status().is_success() {
        let mut body = Vec::new();
        response.body_mut().read_to_end(&mut body).await?;
        let response_message: ChatResponse = serde_json::from_slice(&body)?;
        Ok(response_message)
    } else {
        let mut body = Vec::new();
        response.body_mut().read_to_end(&mut body).await?;
        let body_str = std::str::from_utf8(&body)?;
        anyhow::bail!(
            "Failed to connect to API: {} {}",
            response.status(),
            body_str
        );
    }
}

pub async fn stream_chat_completion(
    client: &dyn HttpClient,
    api_url: &str,
    request: ChatCompletionRequest,
) -> Result<BoxStream<'static, Result<ResponseStreamEvent>>> {
    let uri = format!("{api_url}/chat/completions");
    let request_builder = http::Request::builder()
        .method(Method::POST)
        .uri(uri)
        .header("Content-Type", "application/json");

    let request = request_builder.body(AsyncBody::from(serde_json::to_string(&request)?))?;
    let mut response = client.send(request).await?;
    if response.status().is_success() {
        let reader = BufReader::new(response.into_body());
        Ok(reader
            .lines()
            .filter_map(|line| async move {
                match line {
                    Ok(line) => {
                        let line = line.strip_prefix("data: ")?;
                        if line == "[DONE]" {
                            None
                        } else {
                            match serde_json::from_str(line) {
                                Ok(ResponseStreamResult::Ok(response)) => Some(Ok(response)),
                                Ok(ResponseStreamResult::Err { error, .. }) => {
                                    Some(Err(anyhow!(error.message)))
                                }
                                Err(error) => Some(Err(anyhow!(error))),
                            }
                        }
                    }
                    Err(error) => Some(Err(anyhow!(error))),
                }
            })
            .boxed())
    } else {
        let mut body = String::new();
        response.body_mut().read_to_string(&mut body).await?;
        anyhow::bail!(
            "Failed to connect to LM Studio API: {} {}",
            response.status(),
            body,
        );
    }
}

pub async fn get_models(
    client: &dyn HttpClient,
    api_url: &str,
    _: Option<Duration>,
) -> Result<Vec<ModelEntry>> {
    let uri = format!("{api_url}/models");
    let request_builder = HttpRequest::builder()
        .method(Method::GET)
        .uri(uri)
        .header("Accept", "application/json");

    let request = request_builder.body(AsyncBody::default())?;

    let mut response = client.send(request).await?;

    let mut body = String::new();
    response.body_mut().read_to_string(&mut body).await?;

    anyhow::ensure!(
        response.status().is_success(),
        "Failed to connect to LM Studio API: {} {}",
        response.status(),
        body,
    );
    let response: ListModelsResponse =
        serde_json::from_str(&body).context("Unable to parse LM Studio models response")?;
    Ok(response.data)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_image_message_part_serialization() {
        let image_part = MessagePart::Image {
            image_url: ImageUrl {
                url: "".to_string(),
                detail: None,
            },
        };

        let json = serde_json::to_string(&image_part).unwrap();
        println!("Serialized image part: {}", json);

        // Verify the structure matches what LM Studio expects
        let expected_structure = r#"{"type":"image_url","image_url":{"url":""}}"#;
        assert_eq!(json, expected_structure);
    }

    #[test]
    fn test_text_message_part_serialization() {
        let text_part = MessagePart::Text {
            text: "Hello, world!".to_string(),
        };

        let json = serde_json::to_string(&text_part).unwrap();
        println!("Serialized text part: {}", json);

        let expected_structure = r#"{"type":"text","text":"Hello, world!"}"#;
        assert_eq!(json, expected_structure);
    }
}
